Japanese Patent Publication 3173531 (Patent Document 1) sets forth a position detection method applied to position detection in video camera optics. In this position detection method, the position of the object under measurement is obtained by inputting a sine wave and a cosine wave and processing data. I.e., in this position detection method, an MR sensor (magnetic resistance element) is oriented to oppose an MR sensor magnet in which the S and N poles are alternately magnetized at a position detection magnetizing pitch such that sine and cosinusoidal signals are output from the MR sensor when the MR sensor is moved relative to the magnet. The position of the video camera optics is detected by computing these sinusoidal and cosinusoidal signals.